v4.0

• Bumps to bbl 4.0. This is a breaking change for AWS environments that did not provide the --terraform flag. Follow instructions in the bbl docs for migrating.
• bbl-up task allows the Concourse user to configure the task with an ops-file. This requires a new input called ops-files; if you don't need to provide an ops-file to bbl, map the input to your env-repo and leave OPS_FILES empty.